282 MR. F, E. BEDDARD ON THE [May 4, 
very dissimilar to true nuclei, and the sphere has no limiting mem- 
brane. It is doubtful therefore whether they can be regarded as 
cells, though it is probable that, as the segmentation of the ovum 
advances, the white yolk is directly converted into cells. Now in 
the cell-like bodies which I have described in the immature ovum of 
Lepidosiren there is a very distinct and obvious nucleus (figs. 9-20), 
which is in fact entirely similar to a nucleus of one of the follicular 
cells ; it is deeply stained by borax carmine and unevenly stained, 
so that it has the appearance of being formed of a meshwork of 
condensed protoplasm, the interspaces of which are filled by a 
homogeneous substance which is less acted upon by the reagent. 
In some instances there was more than a single nucleus to each of 
these cells, but it is quite impossible to confound these nuclei with 
the surrounding particles of yolk. Furthermore, in many cases the 
limiting membrane of the cells was distinctly visible (figs. 9 &c.) ; 
and the fact that the cell-contents were hardly acted upon by the 
staining fluid rendered the perception of this membrane easier. 
There seems to he but little doubt that these structures are veritable 
cells, and are not in any way comparable to the white yolk-spheres. 
The question then arises, What is the origin of these cells? Are they 
formed anew within the substance of the ovum, or have they migrated 
from the follicle into the interior of the ovum? 
The former supposition is supported by no facts that I have been 
able to note, and it is distinctly negatived by other facts. 
In the first place, these cells are very closely similar to the cells 
of the follicular epithelium; like them they are bounded by a 
distinct limiting membrane; the contents of both consist of proto- 
plasmic strands and numerous highly refractive particles similar to 
the yolk-particles ; the nucleus is identical in shape and size ; and 
the behaviour of both to the staining reagent is precisely the same. 
This series of facts would, however, be hardly regarded as proof that 
these cells have originated from the’ follicular epithelium; it might 
be supposed that the cells have arisen within the ovum, and that 
some of them have migrated to the periphery to form the follicle, as 
has been stated by various observers to be the case in certain other 
ova (see p. 276); but the immense vascular development round 
the follicular epithelium that has been already mentioned seems to 
indicate that the main activity is centered in these latter cells; and 
this fact, coupled with the additional fact that in certain instances 
there were masses of migrating cells evidently in course of being 
budded off (Plate XXVIII. figs. 5,6) from the follicular epithelium, 
seems to indicate that the second supposition as to the origin of these 
cells is correct, viz. that they are formed by the proliferation of the 
follicular cells and migrate into the interior of the ovary. 
The migration of these cells also explains the absence of a limiting 
membrane to the ovum. A “formed” membrane, however thin, 
would evidently prevent such a migration. 
It appears to me possible to make another statement as a deduction 
from the facts just detailed: that the follicular epithelium-cells 
secrete the yolk which is conveyed to the interior of the ovum by 
